Fail-Safe Function; Damper Control - Honda Prelude 1993 Service Manual

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Fail-sat€ Function:

When the 4WS control unit senses a tailure in the system, it switches to fail-safe mode. In this mode, it powers the tail-

safe and damper relays. The fail-sale relay cuts power to the rear steering motor, while the damper relay slows the

motor's return to neutral. As a result, the rear wheels return slowly to the straight ahead position and then remain there.

The car then drives like conventional 2WS.

When the 4WS control unit switches to fail-safe mode, it stores a Diagnostic Trouble Code (DTC) and turns on the 4WS

indicator light to notify the driver of a problem. This code can be read by connecting the service check connector ter

minals with a iumoer wire under the dash. The code is read as blinks of the 4WS indicator liqht.

4WS INDICATOR LIGHT

Damper Control:

When the system goes into fail-safe mode, it cuts power to the motor by powering the fail-safe relay. Without some type

of damping, the returns springs would turn the rear wheels to the straight-ahead position too rapidly, adversely atlecting

the car's handling.

To counteract this, the 4WS control unit also powers the damper relay. The armature o{ the now deactivated motor is

spun by the movement of the steering shaft. This causes the motor to act as a generator. The voltage generated by this

action is applied back to the motor through the damper relay. This causes the motor to resist the force ot the return spr-

ings. allowing the rear wheels to go back to the straight ahead position slowly.

Troubleshooting